package com.oaker.common.utils;

import java.util.List;

/**
 * @description: 功能描述
 * 功能说明：
 * @className: PageByList
 * @author: sixfly
 * @date: 2023-10-30 0030 12:45
 */


public class PageByList {
    /**
     * 开始分页
     *
     * @param list     传入的list集合
     * @param pageNum  页码
     * @param pageSize 每页多少条数据
     * @return
     */
    public static List startPage(List list, Integer pageNum, Integer pageSize) {
        if (list == null) {
            return null;
        }
        if (list.size() == 0) {
            return null;
        }
        Integer count = list.size(); // 记录总数
        Integer pageCount = 0; // 页数
        if (count % pageSize == 0) {
            pageCount = count / pageSize;
        } else {
            pageCount = count / pageSize + 1;
        }
        int fromIndex = 0; // 开始索引
        int toIndex = 0; // 结束索引
        if (pageNum != pageCount) {
            fromIndex = (pageNum - 1) * pageSize;
            toIndex = fromIndex + pageSize;
        } else {
            fromIndex = (pageNum - 1) * pageSize;
            toIndex = count;
        }
        List pageList = list.subList(fromIndex, toIndex);
        return pageList;
    }
}
